1. Plants and People
Major Families II

2. Poaceae - The Grass Family
Humans devote more than 70% of the Earth’s farmlands
to the production of cereal grains
Grasses provided at least 50% of the world’s caloric
intake
Some anthropologists are of the opinion that the use of
cereal grain was a prerequisite for the formation of a civilization

3. Vegetative Characteristics

4. Grass Inflorescence
The spikelet is the basic unit of grass inflorescence with one or more florets making up the spikelet. The spikelet is subtended by two sterile bracts known as glumes. The glumes define the spikelet, they and everything above them make up the spikelet
Spikelet
Floret
Glumes

5. Floral Morphology
Flowers of the grass family are highly reduced and non-showy and are described using unique terminology
The perianth has been reduced to structures colled lodicules, located at the base of the ovary (these may be absent)
The mature ovary (fruit) is termed grain or caryopsis
Each flower is enclosed by two fertile bracts, with the larger bract, the lemma enclosing the usually smaller bract termed the palea
The tip of a glume, lemma or palea may be extended into a bristle-like structure called an awn
The lemma, palea and the flower make up the floret

6. Floral Morphology An oat spikelet: palea 1 palea 2 awn 1 stigma
anthers
lemma 1
lemma 2
awn 2
glumes

7. The Bean Families
Fabaceae
Caesalpiniaceae
Mimosaceae
Legumes

8. The Bean Families
Everyone agrees that the legumes form a coherent whole based on the presence of a single carpel that matures into a legume.
They can be divided into three groups based on the arrangement and structure of the androecium and perianth, collectively called the androperianth.
The question is whether to :
--treat them all as a single family Fabaceae (broad sense) with three subfamilies or
--treat them as separate families in the order Fabales. This is what we shall do.

9. Fabaceae (strict sense)
Flowers in Fabaceae are zygomorphic and papilionaceous (butterfly-like). The corolla is consists of 5 petals: a banner, 2 wings, and a fused keel. The banner is exterior to the wings.

10. Fabaceae
The fused keel encloses the unique androecium, 10 stamens in 9 fused+ 1 free arrangement (this is termed diadelphous.) The stamens surround the style but are not fused to it.

11. Caesalpiniaceae
Flowers in the Caesalpiniaceae Family are zygomorphic and papilionaceous (butterfly-like). The corolla is consists of 5 petals: a banner, 2 wings, and 2 un-united keel petals. There are 10 stamens that are free and often unalike. The banner is usually located interior to the wings.
banner
wings
keel petals
(not fused)

12. Mimosaceae stamens corolla calyx
Flowers in the Mimosaceae are actinomorphic. Many tiny flowers, each with long, showy stamens, are grouped into globose or elongated inflorescences. These stamens are the showy part of the flower, rather than petals. The corolla is either free or fused.
stamens
corolla
calyx
an individual flower

13. Lab Today
Make sure to examine the oat spikelet dissected for you under one of the microscopes
Sketch your own diagram of the oat spikelet, labeling the important terms, and make sure you understand the different parts of the spiklet!
Compare the sample legume material with information given to you in lecture, paying close attention to the arrangement and structure of the androecium and perianth
Examine the legumes and grains, filling out the table provided for today’s lab